1. Field of the Invention
This invention is generally directed to power transmission systems which are used to link rotary drive input shafts with output shafts or driven elements and more specifically to traction drive systems which utilize surface contact roller elements to divide input loads into multiple power paths to the output shafts or driven elements. The contacting roller elements may include tapered roller elements which will permit the transmission of drive energy or motion to be directed to the output or driven element along a variety of angularly oriented approaches which thereby permits the traction drives of the present invention to have particular utility in transmitting power to helicopter rotors in place of more conventional bevelled gearing, or in hydrofoil propeller drives or "surface effect" (hover craft) which require very high horsepower rates in an angular sense.
2. Summary of the Invention
This invention is directed to multiple roller traction drives which can be used to transmit input motion, energy or power through split power or drive paths to a driven shaft or element regardless of the physical angular relationship the input shaft may have with respect to the output or driven shaft or element. Power from the primary input is transmitted through a first roller member which may be shaped or patterned so as to compensate for any angular approach the input shaft or output shaft may have relative to the energy splitting roller elements. The first roller member is in rotating surface contact with at least one other roller member and both roller members have opposing contact surfaces which frictionally and drivingly engage movable or rotatable contact elements which are carried by the input or output shafts or driven elements. As power is transmitted simultaneously and in opposite directions between the friction drive rollers and the rotatable contact elements which interface an input or output shaft or element therewith, radial stresses on the bearings in which the friction drive rollers are mounted are effectively eliminated or reduced.
In a first embodiment of the invention, power is transmitted through a 90.degree. orientation between the input shaft and an output shaft such as the primary drive shaft or mast for the main rotor of a helicopter. The roller elements of the first embodiment are generally annular in configuration with the input and power splitting rollers having opposing and engaging convex and concave outer surface portions so as to create an elliptical area of contact therebetween.
In a second embodiment of the invention, a friction or traction drive is disclosed having special utility in transmitting power from the motor drive or input shaft of a helicopter to the main rotor drive shaft or mast. As the input shaft is necessarily mounted in an angular relationship with respect to the rotor mast, the traction rollers are bevelled or tapered along their length. In this embodiment, the power splitting roller or rollers are angularly mounted in appropriately positioned bearings so as to enable a continuous surface to surface contact between the input roller and the power splitting roller or rollers. The friction drive rollers are frictionally engaged in opposing directions with bevelled or angled outwardly extending rotary contact elements which are fixedly carried by the rotor mast.
In a third embodiment of the invention, a backdrive traction drive system is disclosed having primary utility in converting and transmitting input from the vertically oriented primary rotor mast or drive shaft to the tail rotor assembly of a helicopter. In this embodiment, power from the main rotor is transmitted through annular outrigger contact elements which are mounted to the rotor mast and which have opposing and slightly concave surfaces which engage with the outer convex surfaces of an output and reactor or power splitting rollers. The rollers are annularly shaped having outer convex surface portions which are angled slightly toward the primary rotor mast or shaft so as to be properly aligned to resist slippage between the surfaces of the outrigger elements and the area of contact with the rollers.
It is the primary object of the present invention to provide traction drives for use in transmitting power between power input shafts and output shafts or driven elements wherein the power is divided or split into alternate load paths to the driven elements so that the contact forces and stresses on any single transmission element are reduced and shared with or distributed to adjacent power transmitting components.
It is another object of the present invention to provide traction drive systems for connecting driven elements or shafts to driving elements or shafts which are angularly disposed in relationship to one another in such a manner that stresses on the connecting or power transmitting drive components are equally balanced so as to reduce the radial or stress loading of the bearings which support such drive components.
It is another object of the present invention to provide traction drives having multiple roller drives which utilize a plurality of roller shapes and wherein power or motion is transferred through surface contact causing elastohydrodynamic films within the roller contact areas.
It is also an object of the present invention to provide a power or motion transmission system for use in connecting a driven element to an input element wherein the power transmission is accomplished through drive traction roller elements so that a substantial reduction is achieved in the operational noise levels inherent in power or motion systems utilizing concentrated bevel gearing.
It is yet another object of the present invention to provide power transmission systems for helicopters, naval or marine vessels or other equipment which are more reliable, quieter and safer than conventional bevel gearing systems and wherein an audible indication is created to alert operators or pilots of potential problems in the transmission system as the failure of traction drive elements will be first evidenced by an increased operational noise level resulting from faulty surface contact elements.
Another object of the present invention is to reduce the cost of manufacturing power transmission systems including those used in helicopters and aircraft, or marine vehicles as traction driven rollers can be produced more easily than bevel gearing which requires cutting and grinding of specific tooth profiles.